Do I have to pick one?
The top book that started me was Rich Dad, Poor Dad by Robert Kiyosaki. It was really scary how much that book just hit me.
I have to say that's the most inspirational because it's the one that really got me started. Since then, I have picked up other books and the following have been inspirational for various reasons.
Richest Man in Babylon by George Clayson - The principles of money that applied in the ancient world of Babylon still apply today. Amazing, isn't it.
Secrets of the Millionaire Mind by T. Harv Eker - The money management system presented in this book was just what I was looking for. You can earn all the money in the world, but without a way to manage it - it means nothing. The other aspect I really like about this book is that it makes you look and recognize at your past programming about money, what your self-stoppers are, and what you can do about it. Be advised this book is a stepping stone for you to sign up for their training programs.
E-Myth Revisited by Michael E. Gerber - You want to tell your boss to shove it and start your own business. The pie baker starts the pie shop. The computer tech opens the computer shop. The plumber starts the contracting service. Before you know it, you're tearing your hair out trying to do everything and all the pies are on the floor. Save yourself the cleanup and learn about systems. This, combined with Cashflow Quadrant (also by Kiyosaki) helps you create a business instead of your own job.
How to Wins Friends & Influence People by Dale Carnegie - All the way from investors to the person sweeping the floor at night, you've got to remember that they are still human beings. They are still people. Treat them all with the same dignity and respect you treat your best friend. These are people you want to build relationships with to last a long time. Treat them well.
Think & Grow Rich by Napoleon Hill - You can have all the technical skills, know the magic of working with people, but it first starts with you. You know that wishes don't make dreams come true, but a burning desire and belief that you can achieve your goals. "Whatever you can conceive and believe, you can achieve." (pg. 14) The only one stopping you IS YOU.